| 摘要 |
PURPOSE:To provide an optical signal input break detecting circuit which can work in a correct way regardless of the variance in the edge number of a received optical signal. CONSTITUTION:A photoelectric converter 1 is provided to convert the received optical signal into an electric signal together with an equalizing amplifier circuit 2 which receives the output signal of the converter 1, and an optical signal input break detecting circuit 7 consisting of a light receiving circuit which includes an identifier 3 which receives the output of the circuit 2, a differential rectifier circuit 4, and a timing extracting filter 5 which extracts a clock signal out of the output of the circuit 4. Furthermore a peak detector 71 is added to receive the output of the filter 5, a signal break deciding circuit 72 which receives the output of the detector 71 at one of its both inputs, and a threshold voltage generating circuit 8 which generates the threshold voltage VTH in response to the change of the edge number of the received optical signal and applies the voltage VTH to the other input of the circuit 72. |
